344 



On the Laieriiic Formation, 



have adhered and not yet sufficiently decoraposed to show the open tex- 

 ture and other features of laterite. This pit at the north end, where it 

 forms the boundary of one of the compounds, confirms me, I think, in 

 the connection between lithomarge and laterite. It is deep and sl'.ows 

 decomposition to a considerable extent ; a rock containing on the surface 

 a bed of quartz has decomposed, and a bed of pebbles for several feet 

 occupies the upper part of the section, with lithomurgic earth beneath, 

 but not well defined, a sort of demi-lithomarge. When the pebba-s have 

 adhered together for some time and decomposition has gone on, and the 

 softer parts fallen away, showing internally a somewhat very slight 

 cavernous aspect, the specimen deserves I think the name of a d( 'rital 

 laterite. The lithomargic, the quartzy and the detrital are well defined 

 by Mr. Cole, page 113 of the 12th Number of this Journal. I prefer 

 extracting Mr. Cole's description, because, without intending by it ta 

 form any classification, he seems to have seen the classification as it 

 existed in nature, at least on the spot described. 



" The laterite varies very much in appearance — sometimes it is very 



hard, compact and heav}', highly ferruginous, of a deep red colour, 

 " penetrated in all directions by the sinuosities containing the red and 



yellow and white earths. Some masses are nearly half composed of 

 " the white lithomargic earth, which renders it very crumbling." Tins- 

 would answer to the lithomargic. " Othei? varieties exhibit a pisiform 

 " structure, numerous rounded pebbles being united together by a yellow 

 " clayey cement; this seems of recent origin." This would answer to the 

 quartzy. " Again, in many superficial situations, it is a mere gravel, pos» 



sessingvery little coherence, and, apparently formed from the dehris of 

 *' the laterite itself. The pebbles composing this gravel, still exhibit the 



structure, of the red conglomerate sand-stone and of the ochrey iron 



ore." This again would answer to the detrital. From this description, 

 and from observation, I have fonned a sort of classification. No doubt 

 there are many kinds of laterite v/hich perhaps cannot come under any of 

 the heads, and I should therefore not wish to claim for it the character 

 of a classification of what exists in nature, but what I have see7i in na- 

 ture — a distinction always necessary, but not always made. 



Water, as an oxydising and decomposing agent, has been men- 

 tioned, but as a transporting one, something may now be said. 

 When a rock has decomposed and the felspar, hornblende, or 

 mica been converted into soil, if much quartz has existed in the 

 i"ock the ground Avill be found in the neighbourhood strewed 

 with small pebbles, which often cover the fields, and during tlie 

 monsoon, when the rush of water is vei y great, all the small water-courses 

 around will be found full of them — these pebbles are carried on to some- 



